The present invention relates to poly(ADP-ribose) glycohydrolases (PARGs) and peptides having poly(ADP-ribose) glycohydrolase activity. In addition, the invention also relates to antibodies, including monoclonal antibodies and antibody fragments, that have specific interaction with epitopes present on poly(ADP-ribose) glycohydrolases. Methods of treatment and diagnosis using the poly(ADP-ribose) glycohydrolases, and antibodies specific for poly(ADP-ribose) glycohydrolases are disclosed. The present invention has implications for the treatment of neoplastic disorder, reperfusion following ischemia, neurological disorders, and related conditions.
Genomic damage, if left unrepaired, can lead to malignant transformation, or cell death by senescence (aging), necrosis or apoptosis. Among the variables that can affect the ultimate biological consequence of DNA damage to a particular cell are (i) the amount, type, and location of the DNA damage and (ii) the efficiency and bioavailability of the cellular DNA repair mechanism.
The activation of poly(ADP-ribose) polymerase (PARP) by DNA strand breaks is often one of the first cellular responses to DNA damage. PARP catalyzes the conversion of nicotinamide adenine dinucleotide (NAD) to multi-branched polymers containing up to 200 ADP-ribose residues. Increases in polymer levels of more than 100-fold may occur within minutes of DNA damage. Once synthesized, polymers are rapidly turned over, being converted to free ADP-ribose by the action of poly(ADP-ribose) glycohydrolase (PARG) (1). An ADP-ribosyl protein lyase has been proposed to catalyze removal of protein-proximal ADP-ribose monomers (2). FIG. 1 illustrates these processes schematically.
The process of activating PARP upon DNA damage can rapidly lead to energy depletion because each ADP-ribose unit transferred by PARP consumes one molecule of NAD, which in turn, requires six molecules of ATP to regenerate NAD. Additionally, NAD is a key carrier of electrons needed to generate ATP via electron transport and oxidative phosphorylation or by glycolysis. The overactivation of PARP due to substantial DNA damage can significantly deplete the cellular pools of NAD and ATP (3). ADP-ribose polymer metabolism, and thus PARP and PARG have been linked to the enhancement of DNA repair (4), limitation of malignant transformation (5), enhancement of necrotic cell death (6), and involvement in programmed cell death (7). To date, studies of the structure and function of the enzymes of ADP-ribose polymer metabolism have been mainly limited to PARP (8). Little is known about the function and regulation of PARG.
As embodied and broadly described herein, the present invention is directed to nucleic acids molecules, peptides, methods, vectors and antibodies that are related to the poly(ADP-ribose) glycohydrolase (PARG) enzyme.
One embodiment of the invention is directed to an isolated and purified nucleic acid molecule or nucleic acid molecule analog comprising a sequence that encodes a polypeptide having poly(ADP-ribose) glycohydrolase (PARG) activity. The nucleic acid molecule may encode the complete full-length PARG gene or a fragment of the PARG gene. The nucleic acid molecule may be DNA, RNA or peptide nucleic acid (PNA). The nucleic acid molecule can be linear, such as, for example, an isolated fragment or a linear phage DNA. In addition, the isolated nucleic acid molecule may be circular, such as for example in a plasmid. The nucleic acid molecule may also be a single stranded DNA or RNA such as the single stranded DNA or RNA in a single stranded DNA virus or single stranded RNA virus. The nucleic acid molecule may be of yeast, insect or mammalian origin.
The nucleic acid molecule of the invention, may be of mammalian origin, such as, for example of bovine or murine origin. In a preferred embodiment of the invention, the nucleic acid molecule may be of human origin. While the sequence of the nucleic acid molecule is of mammalian origin, the nucleic acid molecule may be replicated in another organism such as an insert in a viral genome, a plasmid in a bacterium or a 2-micron plasmid in a yeast.
Preferably, the nucleic acid molecule has, a high degree of sequence similarity with a sequence shown in SEQ ID NO: 1 (Genbank Accession Number U78975), SEQ ID NO: 3 (Genbank Accession Number AF005043), SEQ ID NO: 5 (Genbank Accession Number AF079557), SEQ ID NO: 7 (Genbank Accession Number AF079556) or SEQ ID NO: 9 (Genbank Accession Number CEF20C5). The high degree of sequence similarity may be, for example, about 70%, preferably about 80%, even more preferably about 90% and most preferably substantially identical such as for example about 100% identity.
The nucleic acid molecule that encodes a polypeptide having poly(ADP-ribose) glycohydrolase (PARG) activity may be single or double stranded nucleic acid molecule of any length such as, for example, about 20 bases in length, about 30 bases in length, about 40 bases in length, about 50 bases in length, about 100 bases in length, about 200 bases in length, about 500 bases in length, about 1000 bases in length, about 1500 bases in length, about 2000 bases in length, about 3000 bases in length. It is understood that xe2x80x9cbasesxe2x80x9d in this patent application means xe2x80x9cbasepairsxe2x80x9d when referring to double stranded nucleic acid molecules and bases when referring to single stranded nucleic acid molecules. In a preferred embodiment of the invention, the nucleic acid molecule may be at least about 1000 base or basepairs long and have at least about 80% sequence similarity with a sequence shown in SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 5, SEQ ID NO: 7 or SEQ ID NO: 9.
In one embodiment of the invention, the nucleic acid molecule may have sequence similarity to one region of the PARG sequence. The region may be, for example, from about base residue 2113 to about residue 3105 of SEQ ID NO: 3. Alternatively, the region may be, from residue 1240 to about residue 3105 of SEQ ID NO: 3 or from residue 175 to about residue 3105 of SEQ ID NO: 3.
Another embodiment of the invention is directed to the expression and overexpression of PARG in a cell. Expression vectors may mediate the expression of a polypeptide with poly (ADP-ribose) glycohydrolase (PARG) enzyme activity. Expression systems and expression vectors are known in the art. For example, one expression vector may comprise a regulatory sequence which is operatively linked to a nucleotide sequence at least about 1000 base pairs in length, which has at least 70% sequence similarity with a sequence shown in SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 5, SEQ ID NO: 7 or SEQ ID NO: 9. In a preferred embodiment, the sequence similarity is at least about 80% identity, more preferably at least about 90% identity and most preferably about 100% identity. The expression vector may be any expression vector that is capable of directing expression of a gene in a host cell including, prokaryotic, eukaryotic, mammalian and viral vector. Examples of such vectors include pCMV-Script cytomeglovirus expression vectors for expression in mammalian cells, pESP and pESC vectors for expression in S. pombe and S. cerevesiae, pET vectors for expression in bacteria, pSPUTK vectors for high-level transient expression, and pPbac and pMbac vectors for expression in fall army worm (SF9) cells. Such vectors are available commercially from suppliers such as, for example, Invitrogen (Carlsbad, Calif.) or Stratagene (La Jolla, Calif.) In the use of viral vectors, it is understood that defective viral vectorsxe2x80x94vectors that are genetically engineered to deliver a gene or gene product to a host but which cannot replicate in a host is preferred. Procedures for the practice of in vitro and in vivo expression are well known to those of skill in the art and are further available with the specific expression products and cell lines from commercial suppliers.
Another embodiment of the invention is directed to a host cell transformed with a vector containing a nucleic acid molecule with a sequence that encodes a polypeptide having poly(ADP-ribose) glycohydrolase (PARG) activity. The host cell may be any eukaryotic or prokaryotic cell such as, for example a human, murine, rattus, bovine, insect, yeast or bacteria. Specific cell lines are well known to those of skill in the art and are available from suppliers such as the American Tissue Type Collection (ATCC, Manassas, Va.) and Stratagene (La Jolla, Calif.) and the like. A preferred embodiment of the invention is directed to cells transformed with the PARG expression vector which shows an elevated level of PARG relative to non-transformed cells. Especially preferred are cells transformed with an inducible PARG expression vector that have normal or slightly elevated PARG levels before induction and have significantly elevated PARG levels after induction.
An embodiment of the invention is directed to an isolated protein having poly(ADP-ribose) glycohydrolase (PARG) activity. The protein may comprise an amino acid sequence with at least 70% sequence similarity with a sequence shown in SEQ ID NO: 2 (Genbank Accession Number U78975), SEQ ID NO: 4 (Genbank Accession Number AF005043), SEQ ID NO: 6 (Genbank Accession Number AF079557), SEQ ID NO: 8 (Genbank Accession Number AF079556), or SEQ ID NO: 10 (Genbank Accession Number CEF20C5). The sequence similarity is preferably at least about 80%, more preferably at least about 90% and most preferably substantially identical with a sequence shown in SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, or SEQ ID NO: 10. In a preferred embodiment of the invention, the preferred isolated protein having poly(ADP-ribose) glycohydrolase (PARG) activity and has a molecular weight greater than about 100 kDa.
Another embodiment of the invention is directed to an oligonucleotide which is greater than about 10 bases in length and less than about 1000 bases in length which is complementary to a sequence shown SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 5, SEQ ID NO: 7, or SEQ ID NO: 9. The oligonucleotide may be, for example, greater than about 20 bases in length, greater than about 30 bases in length, greater than about 40 bases in length, greater than about 50 bases in length, greater than about 100 bases in length, greater than about 200 bases in length or greater than about 300 bases in length. The oligonucleotide, which may be optionally labeled with a detectable marker, may be DNA, RNA or PNA. A detectable marker may be, for example, a radioactive isotope such as 32P or 125I, an epitope such as FLAG.
One preferred oligonucleotide is an antisense oligonucleotide directed to the mRNA of PARG. Antisense oligonucleotide as a method of suppression is well known to those in the art. For example, the phosphorothioate oligonucleotide, ISIS 2922, has been shown to be effective against cytomeglovirus retinitis in AIDS patients (9). It is thus well known that oligonucleotides, when administered to animals and humans, can have a useful therapeutic effect. In a preferred embodiment, the oligonuclcotide is at least about 10 nucleotides in length, such as, greater than about 20 bases in length, greater than about 30 bases in length, greater than about 40 bases in length, greater than about 50 bases in length, greater than about 100 bases in length, greater than about 200 bases in length or greater than about 300 bases in length. In another preferred embodiment, the oligonucleotide has a ribozyme activity.
Another embodiment of the invention is directed to an isolated polypeptide of at least 6 amino acid residues in length and having a molecular weight less than about 65 kDa, which has at least about 80% sequence similarity with a sequence shown in any one of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8 or SEQ ID NO: 10. The polypeptide may be, for example, at least about 10 amino acids in length, at least about 20 amino acids in length, at least about 30 amino acids in length, at least about 40 amino acids in length, at least about 50 amino acids in length, at least about 75 amino acids in length, at least about 100 amino acids in length, at least about 150 amino acids in length, at least about 250 amino acids in length or at least about 500 amino acids in length or more.
In a preferred embodiment, the polypeptide has a molecular weight less than about 40 kDa and has at least about 90% sequence similarity with a sequence shown in any one of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8 or SEQ ID NO: 10. The polypeptide preferably has poly(ADP-ribose) glycohydrolase (PARG) activity or is immunogenic and elicits antibodies immunoreactive with a poly(ADP-ribose) glycohydrolase (PARG) enzyme. In a more preferred embodiment, the polypeptide comprises an amino acid sequence substantially identical with SEQ ID NO: 4 from about residue 647 to about residue 977.
Another embodiment of the invention is directed to an isolated polypeptide of at least 10 amino acid residues in length and which has at least about 80% sequence similarity with a sequence shown in any one of SEQ ID NO: 2, SEQ ID NO 4, SEQ ID NO: 6, SEQ ID NO: 8 or SEQ ID NO: 10. Preferably, the polypeptide is at least about 20 amino acids in length, such as, for example at least about 30 amino acids, about 40 amino acids, about 50 amino acids, about 100 amino acids, about 200 amino acids and about 500 amino acids in length.
Another embodiment of the invention is directed to an antibody immunoreactive with an isolated polypeptide of at least about 6 amino acid residues in length and having a molecular weight less than about 65 kDa, which has at least about 80% sequence similarity with a sequence shown in any one of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8 or SEQ ID NO: 10. In a preferred embodiment, antibody is immunoreactive with a polypeptide with a molecular weight less than about 40 kDa and has at least about 90% sequence similarity with a sequence shown in any one of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8 or SEQ ID NO: 10. In another preferred embodiment, the antibody is immunoreactive with a polypeptide comprising an amino acid sequence substantially identical with SEQ ID NO: 4 from about residue 647 to about residue 977.
Another embodiment of the invention is directed to a method of detecting a polypeptide having PARG activity comprising the steps of contacting the polypeptide with an antibody immunoreactive with an isolated polypeptide of at least about 6 amino acid residues in length and having a molecular weight less than about 65 kDa, which has at least about 80% sequence similarity with a sequence shown in any one of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8 or SEQ ID NO: 10, and determining whether the antibody immunoreacts with the polypeptide.
Another embodiment of the invention is directed to a method of preventing, treating, or ameliorating a disease condition or disorder in an individual comprising the step of administering a therapeutically effective amount of a poly(ADP-ribose) glycohydrolase (PARG) inhibitor or activator to the individual. The disease condition or disorder may be any condition associated with responses to DNA damage, examples of which include a neoplastic disorder, a myocardial infarction, a vascular stroke or a neurodegenerative disorder. The PARG inhibitor or activator may be a small molecule inhibitor or activator of PARG or may be an antisense oligonucleotide that can hybridize in vivo to messenger RNA encoded by a PARG gene. PARG based treatment may be directed to new methods for preventing, treating or ameliorating disorders associated with DNA damage. These disorders include neoplastic disorders, inborn genetic errors, myocardial infarctions, vascular strokes, aging, and neurodegenerative disorders such as Alzheimer""s disease, Huntington""s disease, Parkinson""s disease, and neurotoxicity generally.
Another embodiment of the invention is directed to the identification of novel PARG modulators which can activate or inhibit DNA repair and/or apoptosis. A PARG modulator is a compound that can activate or inhibit PARG. These modulators are preferably more efficacious and do not have the known side effects of present modulators. One method of identifying an agent that inhibits or activates poly(ADP-ribose) glycohydrolase (PARG) activity comprise the steps of providing a liquid medium that contains a polypeptide having PARG activity contacting the polypeptide with a candidate agent, in the presence of a reference compound having affinity for the polypeptide, under predetermined assay conditions, and determining the affinity of the candidate agent for the polypeptide relative to the reference compound. Thus, the modulation activity of the candidate agent relative to the reference compound is determined. In this method, the polypeptide may be immobilized on a solid support. Further, the polypeptide may be generated in vitro by culturing a cell transformed with a nucleic acid molecule encoding PARG under conditions effective to express the polypeptide.
Another embodiment of the invention is directed to a method of identifying a mutant PARG allele in an individual comprising the step of obtaining genomic material from the individual; digesting the genomic material with a restriction enzyme having a recognition site inclusive of the mutant allele; fractionating the restriction fragments obtained from the digestion; and comparing the fractionation pattern with that obtained for a normal allele, thereby determining the presence or absence of the mutant allele. The fractionating step may be performed with electrophoresis.
Another embodiment of the invention is directed to a method of identifying a mutant PARG allele in an individual comprising the steps of hybridizing an oligonucleotide with genomic material from the individual, which oligonucleotide hybridizes under predetermined hybridization conditions to a region immediately 5xe2x80x2 of a predetermined mutation site in the PARG alleles with the 3xe2x80x2 terminus of the oligonucleotide complementary to an unmutated PARG allele; extending the oligonucleotide using PCR amplification; and determining the degree to which extension occurs, thereby determining the presence or absence of the mutant allele. The PCR extension reaction may be performed at a temperature above about 50xc2x0 C. The determination may be performed by conducting electrophoresis (using for example, acrylamide at about 4% to about 10% or agarose and low melting temperature agarose from about 0.8% to about 4%) on the products of PCR amplification.
Another embodiment of the invention is directed to a method of screening molecules for PARG modulating activity (inhibition or activation) comprising the steps of providing a purified PARG enzyme; assaying the enzyme in the presence of a molecule to be screened; and comparing the activity of the PARG enzyme in the presence of the molecule to the activity of the PARG enzyme in the absence of the molecule.
Another embodiment of the invention is directed to a method of gene therapy comprising the step of delivering an oligonucleotide having a sequence complementary to at least a portion of a polynucleotide encoding a PARG enzyme to a cell to be treated. In the method, the oligonucleotide may have a sequence complementary to a sequence encoding a C-terminal portion of a PARG enzyme. Further, in the gene therapy method, the oligonucleotide may further comprise a ribozyme.
Another embodiment of the invention is directed to a method of delivering to a cell surface, an oligonucleotide having a sequence complementary to at least a portion of a polynucleotide encoding a PARG enzyme to a cell to be treated. In the method, the oligonucleotide may have a sequence complementary to a sequence encoding a C-terminal portion of a PARG enzyme. Further, in the method, the oligonucleotide may further comprise a ribozyme. The portion of a polynucleotide encoding a PARG enzyme may be, for example, the polynucleotide encoding the N terminus third of PARG, the middle third of PARG, or the C terminus third of PARG. The portion of a polynucleotide may encode a smaller part of PARG such as the N terminus 10% of PARG, the C terminus 10% of PARG, or any 10% portion in between such as from 10% to 20%, from 20% to 30%, from 30% to 40%, from 40% to 50%, from 50% to 60%, from 60% to 70%, from 70% to 80%, from 80%/ to 90%. The percent value used means a percent of the linear amino acid sequence. Thus, for a 1000 amino acid protein, the N terminus 10 percent is from amino acid 1 to 100; 10% to 20% percent would be from amino acid 100 to 200 and so on. For a 970 amino acid protein, the N terminal 10% would be from amino acid 1 to 97; 10% to 20% would be from amino acids 98 to 194 amino acids.
Another embodiment of the invention is directed to a method of sensitizing a cell to a chemotherapeutic agent comprising the step of contacting the cell with a molecule that modulates the activity of a PARG enzyme. The molecule may be an oligonucleotide having a sequence complementary to at least a portion of a polynucleotide encoding a PARG enzyme. For example, the oligonucleotide may have a sequence complementary to a sequence encoding a C-terminal portion of a PARG enzyme. The portion of a polynucleotide encoding a PARG enzyme may be, for example, the polynucleotide encoding the N terminus third of PARG, the middle third of PARG, or the C terminus third of PARG. The portion of a polynucleotide may encode a smaller part of PARG such as the N terminus 10% of PARG, the C terminus 10% of PARG, or any 10% portion in between such as from 10% to 20%, from 20% to 30%, from 30% to 40%, from 40% to 50%, from 50% to 60%, from 60% to 70%, from 70% to 80%, from 80% to 90%. The oligonucleotide may further comprise a ribozyme. The method may be used, for example, as a method of treating a diseased cell characterized by the presence of DNA strand breaks. In the treatment, the cell is contacted with a molecule that modulates an enzymatic activity of a PARG enzyme.
Another embodiment of the invention is directed to a pharmaceutical composition comprising an oligonucleotide having a sequence complementary to at least a portion of a polynucleotide encoding a PARG enzyme. The produced molecule may be an oligonucleotide having a sequence complementary to at least a portion of a polynucleotide encoding a PARG enzyme. For example, the oligonucleotide may have a sequence complementary to a sequence encoding a C-terminal portion of a PARG enzyme. The oligonucleotide may comprise a ribozyme activity.
Another embodiment of the invention is directed to a virus that causes the production of all oligonucleotide having a sequence complementary to a polynucleotide encoding a PARG enzyme. This may be, for example, a viral vector which after the infection of a host cell, causes the production of an antisense RNA of PARG. The molecule may be an oligonucleotide having a sequence complementary to at least a portion of a polynucleotide encoding a PARG enzyme. For example, the oligonucleotide may have a sequence complementary to a sequence encoding a C-terminal portion of a PARG enzyme. The oligonucleotide may further comprise a ribozyme activity.
Other embodiments and advantages of the invention are set forth, in part, in the description that follows and, in part, will be obvious from this description and may be learned from the practice of the invention.